Note: This column is for information purposes only and is not intended as a substitute for professional medical advice.

Q: In the summer of 1956, I had a fever, stiff neck, and my legs became paralyzed for a week. Our family doctor diagnosed rheumatic fever since I had been given the Salk polio vaccine and therefore couldn't have had polio. My legs recovered their strength in a few months. Over the past five years my legs are becoming weaker. I went to a well-known post-polio doctor who said I couldn't have had polio because there were no cases after the vaccine came out in 1954. Then I went to a rheumatologist who said I'd never had rheumatic fever. How can I know if I had polio, what is causing my new problems and what can I do about them?

A: It's impossible to know for sure what paralyzed your legs in 1956. But polio is the most likely suspect. The polio vaccine was not 100-percent effective. And polio wasn't eliminated by the vaccine. There were over 15,000 reported cases of polio in the United States in 1956. So you very well could have had polio.

People who are having symptoms that sound like PPS but who don't have a positive diagnosis of polio often ask us if there are tests to prove they'd had polio. For those who never received the polio vaccine, measuring antibodies to the three types of polioviruses would show an increase indicating the poliovirus that had infected you. It is also possible, whether you had the vaccine or not, to have a biopsy, where a small chunk of muscle is removed to look for signs of motor neurons having died, which could have been--but isn't necessarily--the result of a poliovirus attack.

The most readily available test is an EMG, where a needle is inserted into a muscle to look for a pattern of electrical activity that indicates motor neurons had been killed. However, an EMG can't say if it was polio that killed the neurons. What's more, an EMG isn't always positive in those who were known to have had polio. In 1991 physiatrist Mark Bromberg found that almost 10 percent of patients who had a history of paralytic polio, and who were reporting new pain, fatigue or weakness in mid-life, had normal EMGs.

In spite of this research, it has been suggested that every polio survivor have an EMG to identify muscles that weren't affected by polio so that vigorous exercise can be prescribed without worrying that muscles will weaken. One study found that almost a quarter of paralytic polio survivors' limbs had no EMG evidence of motor neurons having been killed. Those limbs were classified as having "no clinical polio" and therefore could be strenuously exercised.

However, using a special EMG technique not available in doctors' offices, neurologist Carlos Luciano found evidence of poliovirus damage in 85 percent of muscles that were thought to have had "no clinical polio." This makes sense, since research from the 1940s by polio pioneer David Bodian--and a 1997 study by neurophysiologist Alan McComas--showed that polio survivors' seemingly unaffected muscles lost 40 percent of their motor neurons. So, polio survivors' muscles can be "silently affected" and develop weakness without any obvious evidence of poliovirus damage.

The danger of using an EMG to diagnose polio or identify "unaffected" muscles is seen in the experience of one of our patients, whose legs had been weakened by polio and were getting weaker, causing him to use crutches. He wanted to know if polio had affected his arms since he wanted to take a "walking tour" of Europe. He asked for an EMG of his arm muscles, which showed "no clinical polio." Off he crutched through Europe, where his arms became weak. He returned a month later barely able to lift them. The moral is that an expensive and very painful EMG is neither reliable nor desirable if you're trying to decide if a muscle had been affected by polio.

So what should you do if you have new weakness, can't prove you had polio, or aren't certain the poliovirus affected a given muscle? If you and your doctor are certain that nothing else is causing new weakness, the safest thing to do is assume that every muscle was somewhat affected by polio and take care of them all by following "The Golden Rule"--If anything causes fatigue, weakness or pain, DON'T DO IT (or do much less of it).